Various arrangements have been used to provide a mounting for a lens so that the lens may be moved or adjusted axially along the optical axis. For example, U.S. Pat. No. 3,138,060 to Eggert, et al, June 23, 1964 for "Clamping Means for Variable Focal Length Projector Objective Lens" shows how a helical slot in a lens mounting may be used with a pin cammed in the slot to give an axial motion to the lens. U.S. Pat. No. 3,399,015 to Jacobs Aug. 27, 1958 for "Mounting Mechanism for Zoom Magnifier" shows a pin which slides in a camming helical slot, two other slots in which another pin rides, and rotation if a sleeve cams the lens to follow an axial path.
U.S. Pat. No. 4,090,780 to Davis May 23, 1978 for "Linear Objective Adjustment Device for Rifle Scope Collimation" describes a lens mount slidable axially and sealed by an O-ring, or the like, from the atmosphere to retain a nitrogen gas interior.
U.S. Pat. No. 4,269,479 to Hamatani, Jan. 22, 1979 for "Mounting System for Optical Lens Assembly" shows a lens mounting with lubricating means by way of resilient elements.